1. Field of the Invention
The present invention relates to a fixation film for fixing toner using heat generated by inducing an eddy current with electromagnetic induction. More particularly, this invention relates to a fixation film suitable for a toner fixing apparatus for fixing toner, which is employed in an image formation apparatus such as an electrophotographic apparatus and electrostatic recording apparatus. The present invention also relates to a toner fixation apparatus using the above fixation film.
2. Related Background Art
Contact heating systems such as a heat roller system and a film heating system have been widely used as a heating system represented by a toner fixation apparatus.
Among the toner fixation apparatuses, the color toner fixation apparatus which fixes four toner layers at maximum uses a halogen heater as a heat generator to heat the toner image via the core metal and the elastic rubber layer of a fixing roller.
Japanese Patent Publication No. 5-9027 has discloses a heating method utilizing Joule heat caused by an eddy current induced by a magnetic flux within a fixation roller.
When heat is generated by eddy current induction, the heat generation site can be made close to the toner. Thus, the energy consumption efficiency can be greatly improved in comparison with a heat roller using a halogen lamp.
However, according to the method taught in Japanese Patent Publication No. 5-9027, even the most efficient fixation roller cannot achieve quick start since a fixation roller having a large heat capacity is heated. In that case, since the temperatures of the exciting coil and the exciting iron core are also raised, the amount of magnetic flux is decreased and heat generation becomes unstable. Furthermore, heat efficiency is not satisfying because of the heat dissipation into the roller.
In an effort to overcome the foregoing problems, a method of inducing an eddy current within a metallic film and thus generating Joule heat has been proposed recently. However, the method using the metallic film has a limit in heat generation capacity. If the metallic film is made thicker in order to increase the heat generation, the metallic film becomes very rigid, so that, when the metallic film is used as a fixation film, problematically the fixation film can not be curved to enable "curvature separation," that is, separation of the fixation film from a recording material (or transfer material) by increasing curvature.